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Carbon Dioxide Sorbents with Propylamine Groups-Silica Functionalized with a Fractional Factorial Design Approach
Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
2011 (English)In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 27, no 7, 3822-3834 p.Article in journal (Refereed) Published
Abstract [en]

Mesoporous silica particles (Davisil) were functionalized with aminopropyltriethoxysilane (APTES) in a fractional factorial design with 19 different synthesis and uptake experiments. The number of amino groups and the uptake of CO(2) were optimized in a 2(V)(5-1) design. Most important to functionalizationwas the amount of water present during synthesis, the reaction time, and pretreating the silica with a mineral acid; certain two-way interactions were shown to be statistically significant as well. Modifications performed at 110 or 80 degrees C showed no significant differences concerning amine content or uptake of CO(2). Properly choosing center points for the discrete variables is problematic and is somewhat related to the lack of fit with respect to CO(2) uptake; the regression was good. Solid-state (29)Si NMR showed that the APTES was mainly fully condensed. Specific surface areas did not correlate with the number of n-propylamine groups on the silica, which is indicative of differential levels of heterogeneity in the coverage of propylamines. The uptake of CO(2) and N(2) was measured from -20 to 70 degrees C and from 0 to 1 bar and parametrized by the Freundlich isotherm. Amine-modified silica adsorbed significant amounts of CO(2), especially at the low partial pressure, which is important for CO(2) capture from flue gas. At such pressures, samples with a high density of amine (4 amines/nm(2)) showed a much higher uptake of CO(2) than did those with densities of similar to 2-3 amines/nm(2), reflecting differential tendencies to form propylammonium-propylcarbamate ion pairs; these require close proximity among amine groups to form. Water affected the uptake of carbon dioxide in different ways. Certain samples took up more moist CO(2) gas than dry CO(2), and others took up less moist CO(2) than dry CO(2), which is indicative of differential tendencies toward water adsorption. We conclude that experimental design is a time-efficient approach to the functionalization of silica with propylamine groups.

Place, publisher, year, edition, pages
2011. Vol. 27, no 7, 3822-3834 p.
National Category
Materials Chemistry
Research subject
Materials Chemistry
Identifiers
URN: urn:nbn:se:su:diva-68812DOI: 10.1021/la104629mISI: 000288970900079OAI: oai:DiVA.org:su-68812DiVA: diva2:474300
Note
3Available from: 2012-01-09 Created: 2012-01-07 Last updated: 2017-12-08Bibliographically approved
In thesis
1. Synthesis and modification of potential CO2 adsorbents: Amine modified silica and calcium carbonates
Open this publication in new window or tab >>Synthesis and modification of potential CO2 adsorbents: Amine modified silica and calcium carbonates
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The prospect of rapid changes to the climate due to global warming is subject of public concern. The need to reduce the emissions of atmospheric green house gases and in particular carbon dioxide is greater than ever. Extensive research is performed to find new solutions and new materials, which tackles this problem in economically benign way. This thesis dealt with two potential adsorbents for post combustion  carbon capture, namely, amine modified silica and calcium carbonates. We modified porous silica with large surface area by propyl-amine groups to enhance the carbon dioxide adsorption capacity and selectivity. Experimental parameters, such as reaction time, temperature, water content, acid and heat treatment of silica substrate were optimized using a fractional factorial design. Adsorption properties and the nature of formed species upon reaction of CO2 and amine-modified silica were studied by sorption and infrared spectroscopy. Physisorbed and chemisorbed amount of adsorbed CO2 were, for the first time, estimated directly in an accurate way. The effects of temperature and moisture on the CO2 adsorption properties were also studied.

Crystallization of calcium carbonate as a precursor to calcium oxide, which can be used as carbon dioxide absorbent, was studied in the second part of this thesis. Structure of different amorphous phases of calcium carbonate was studied in detail. Crystallization of calcium carbonate with and without additives was studied. Parameters like stirring rate, temperature, pH and polymer concentration showed to be important in selection of phase and morphology. An aggregation mediated crystallization was postulated to explain the observed morphologies. 

Place, publisher, year, edition, pages
Stockholm: Department of Materials and Environmental Chemistry (MMK), Stockholm University, 2012. 87 p.
Keyword
Amine-modified silica, carbon capture, Fractional factorial design, IR spectroscopy, calcium carbonate
National Category
Materials Chemistry
Research subject
Materials Chemistry
Identifiers
urn:nbn:se:su:diva-75638 (URN)978-91-7447-516-6 (ISBN)
Public defence
2012-06-05, Magnélisalen, Kemiska övningslaboratoriet, Svante Arrhenius väg 16 B, Stockholm, 13:00 (English)
Opponent
Supervisors
Note
At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 3: Accepted.Available from: 2012-05-10 Created: 2012-04-24 Last updated: 2012-04-30Bibliographically approved

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